Sealing device for rotary mechanisms

ABSTRACT

In a rotary mechanism of the Wankel type, a sealing device for each of the apex portions of the rotor which sealing device comprises a seal blade disposed for reciprocation toward and away from the trochoidal surface of the mechanism housing and a pressurized fluid actuating means responsive to the angular velocity of the rotor and coacting with the seal blade to hold the latter out of engagement with the trochoidal surface at a predetermined rotor angular velocity.

United States Patent 1 Woodier et al.

[451 Mar. 12,1974

1 1 SEALING DEVICE FOR ROTARY MECHANISMS [75] Inventors: George H.Woodier, Ringwood;

4 Winthrop B. Pratt, North l-laledon,

both of NJ.

[73] Assignee: Curtiss-Wright Corporation,

Wood-Ridge, NJ.

22 Filed: Mar. 30, 1973 211 App1lNo.:346,638'

[52] US. Cl 418/115,4l8/123,4l8/l24, V 277/28 [51] Int. Cl. F01c 19/02,F04c 15/00, F040 27/00 [58] Field ofSearch 418/84,93, 113, 115,418/122-121, 277/28 [56] References Cited UNITED STATES PATENTS3,229,673 1/1966 Ehrhardt 418/123 Jones et a1. 418/115 3,456,626 7/1969418/115 3,482,551 7 12/1969 418/115 3,496,916 2/1970 418/1 15 3,721,5103/1973 Gilbert 418/115 Primary Examiner-Carlton R. Croyle AssistantExaminer.lohn J. Vrablik Attorney, Agent, or Firm-Arthur Frederick [5 7ABSTRACT In a rotary mechanism of the Wankel type, a sealing device foreach of the apex portions of the rotor which sealing device comprises aseal blade disposed for reciprocation toward and away from thetrochoidal surface of the mechanism housing and a pressurized fluidactuating means responsive to the angular velocity of the rotor andcoacting with the seal'blade to hold the latter out of engagement withthe trochoidal surface at a predetermined rotor angular velocity.

16 Claims, 4 Drawing Figures SEALING DEVICE FOR ROTARY DISCLOSURE Thisinvention relates to sealing devices for rotary mechanisms and, morespecifically, pertains to sealing devices disposed at the apex portionsof the rotors of rotary mechanisms of the Wankel type such as disclosedin the U.S.'Pat. to Wankel et al., No. 2,988,065.

BACKGROUND or THE- INVENTION It is well-known in rotary mechanisms thatit is desirable to minimize friction between the rotor and housingwithin which the rotor rotates and that diminution of friction can beaccomplished at relatively high angular velocities of the rotor withouta material penalty in efficiency by retraction of the seals away fromthe station- I ary housing wall surface. Such sealing devices whichautomatically adjust the position of the sealing devices in accordancewith the angular speed of the rotor are exemplified in the following'U.S. Pat. Nos.:

1,158,733 Shepard et a1.; 2.041,]21 Fareso, Sr.; 3,229,673 Ebrha'rdt;3,444,843 Sabet; 3,456,625 Jones et al.; 3,456,626 Jones; 3,482,551Jones; 3,496,9l6-Jones; 3,707,340 Brille. I

In rotary mechanisms of the Wankel type in which a rotor rotates withina housing cavity defined by end walls and an inner trochoidal wallsurface, the trochoiweighls are employed to retract a'seal blade in adirection away from the trochoidal surface by overcoming the centripedalacceleration forces acting on the seal blade, it is necessary to providein the interconnection between the flyweights and seal blade a lostmotion to prevent the seal blade from re-engaging the trochoidal surfacedue to the change in direction of the centripedal acceleration forcesacting on the flyweights. Thus, in such sealing devices the lost motionresults in clatter and possible excessive wear of the seal bladecomponents.

It is therefore an object of this invention to provide in a rotarymechanism of the Wankel type a sealing device carried by a rotor whichsealing device automatically holds the seal blade out of engagement withthe trochoidal sealing surface at a predetermined angular speed of therotor and retains the seal blade out of engagement for the entire lengthof the trochoidal sealing surface until the angular speed of the rotorfalls below the predetermined value.

Another object of the present invention is to provide in a rotarymechanism of the Wankel type a sealing'device carried by a rotor whichsealing device is capable of holding the seal away from the trochoidalsealing surface without the use of relatively complex pivotal linkagesand flyweights.

A further object of this invention is to provide in a rotary mechanismof the Wankel type a sealing device carried by a rotor, which sealingdevice responds to a fluid pressure, the magnitude of which is afunction of the angular velocity of the rotor. I

SUMMARY OF THE INVENTION In a rotary mechanism of the Wankel type, arotor is eccentrically mounted on a crankshaft for rotation in a cavityformed by the mechanism housing. The rotor has a plurality of apexportions. The flank portions of the rotor and the trochoidal shapedperipheral wall surface of the housing cavity, taken together, define aplurality of working chambers which successively increase and decreasein volumetric size as the rotor rotates. The rotor. has, at each apexportion, an apex sealing device according to this invention whichincludes a seal blade means sealingly sweeping the peripheral wallsurface and radially movable relative to the rotor for maintainingsealing engagement with the peripheral wall surface. The apex sealingdevice also includes a pressurized fluid actuating means responsive to apredetermined rotor angular velocity and coacting with the seal blademeans to remove the contact pressure of the seal blade means against theperipheral wall surface and hold the seal blade means away from theperipheral wall surface as rotor speed increases beyond thepredetermined angular velocity. This source of pressurized fluid may bethe bearing lubricant fluid which may be circulated by means of apositive displacement pump such as a gear pump, driven by the crankshaftas disclosed in the US. Pat. to Jones et :al., No. 3,359,952, or someother suitable means providing a fluid pressure which varies as afunctionof rotor speed such as the change in fluid pressure due tocentrifugal force acting on the column of lubricating oil in passagewaysextending radially in the shaft eccentric and rotor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 2 is a view in cross-sectiontaken substantially along line 22 of FIG. 1 on an-enlarged scale;

FIG. 3 is a cross-sectional view taken substantially along line 33 ofFIG. 2; and

FIG. 4 is an isometric view of the collar forming part of the sealingdevice of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to the drawingsand more particularly to FIG. 1, the. reference number 10 generallydesignates a rotary mechanism ,of the Wankel type which has a rotor 12,the apices 14 of which carry sealing devices 16 according to thisinvention. The rotary mechanism 10 for illustration purposes only isshown as an internal combustion rotary engine and it is therefore to beunderstood that the invention is not limited thereto. The rotarymechanism without departure from the scope and spirit of the inventionmay be applicable to other rotary mechanisms, such as compressors, pumpsand expansion engines.

As shown in FIG. 1, rotary mechanism 10 comprises, in addition to rotor12, a housing 18 defining a cavity which has a peripheral wall surface20 of epitrochoidal on a crankshaft 22 to effect rotation of the latterthrough an eccentric portion 24 of the crankshaft. The housing cavityhas two lobes while rotor 12 hasthree peripheral surfaces or flanks 26which define with housing 18 three working chambers 28. The workingchambers 28 successively increase and decrease in volumetric size asrotor 12 eccentrically rotates within the housing cavity. A fluid intakeport 30 is provided to pass combustible gaseous fluid into the workingchamber during a suction or intake phase of operation. After thecompression phase of operation, the gaseous fluid is ignited by anignition means, such as spark plug 32. An exhaust port 34 is provided sothat on the exhaust phase of operation the products of combustion can beexpelled, from the working chambers. To maintain working chambers 28 outof communication with each other, rotor 12 carries, in addition tosealing devices 16, a plurality of seal strips 36. The seal strips 36are located in each of the side faces 38 of rotor 12 and function toseal thespace between the side faces and the adjacent end wall 37 ofhousing 18. The sealing devices 16 serve to seal the space between eachrotor apex portion 14 and trochoidal surface of housing 18.

As best shown in FIGS. 2 to 4, each of the sealing devices 16 comprisesa seal blade means 40 mounted for reciprocative movement in a slot 42 inthe apex portion 14 of rotor 12 and fluid pressurized actuating means 44coacting with the seal blade means.

The blade means 40 is preferably, as shown, a single blade element whichhas two spaced leg portions or tabs 46. Each of the tabs 46 is disposedinwardly of and adjacent to the apex seal pin 48 and extend radiallyfrom the inner edge of blade means 40 through a radially extending slot50. The slot 50 communicates, at one end,'with slot 42 and at theopposite end, with an axially extending bore 52 in the apex portion ofrotor 12. A biasing means, such as a flat spring 54, is disposed betweenthe bottom of slot 42 and the inner edge of blade means 40 to urge theblade means toward trochoidalsurface 20. While blade means 40 is shownas a single blade element, the blade means may be a multiblade assembly,such as disclosed in the US. Pat. to Jones, No. 3,400,691, withoutdeparture from the scope andspirit of this invention.

The fluid pressurized actuating means 44 comprises two pistons 56, eachof which is disposed for reciprocation in a counterbored portion orpiston-cylinder 58 of bore 52. Each piston 56 has an axially extendingarm 60 which is bifurcated at its distal end to embrace an associatedtab 46. Each arm 60 has camming edges 62 which are inclined radiallyoutward in a direction toward distal end and engages a pin 64 carried intab 46 of blade means 40. Each of the pistons 56 is biased inwardly awayfrom the rotor side faces 38 by a helical spring 66. One end of thespring bears against the piston and the other end against a collar 68which is disposed in bore 52. The collar 68 is secured in bore 52 by asplit ring 70 which bears against a disc-shaped cover element 72. Thecover element 72 fits against collar 68 in a fluid tight manner toprevent passage of gas or liquid from bore 52.

As best shown in, FIG. 4, collar 68 is cylindrical and has a diametraldimension so that it is snugly receivable in bore 52. A longitudinallyextending diametral slot 74 is provided in collar 68. The slot 74 is ofsuch width as to receive therein the bifurcate distal end portion ofpiston arm 60' (see FIG. 2) and pin 64. A second diametral'slot 76 isprovided in collar 68 which slot 76 communicates with slot 74 throughthe bottom wall 75 of slot 74. The slot 76 is substantially narrower inwidth than slot 74 and, when the collar is properly positioned inbore52, it is in register with slot 50 so that tab 46 of blade means 40can project from slot 50 into slot 74. The slot 76 together with slot 50serve to guide tab 46 in its slidable movement relative to rotor 12. v

The pistons 56 are subject to fluid pressure in a pressure chamber 78which is defined between the pistons 56 and another counterbored portion80 of bore 52. To seal the interstices between the pistons and pistoncylinders 58, each piston is provided with O-ring seals 79 or othersuitable sealing means. The pressure chamber 78 is in communication witha suitable source of pressurized fluid through a supply passageway 82.As

. shown, such source of pressurized fluid may be bearing I rotor speedand, therefore, if the pressurized fluid is lubricating oil, the oilpump (not shown) may be driven by the crankshaft as is disclosed inthe-US. Pat. to-

Jones et al., No. 3,359,952. However, it is within the purview of thepresent invention to employ any suitable source of pressurized fluid,the pressure of which varies with rotor rpm. For example, the change inoil pressure in passageways 82 and 84 due to the centrifugal forceacting thereon as rotor 12 rotates, may be utilized to provide apressure in chamber 78 which varies as a function of rotor speed.

In operation of rotary mechanism 10, each of the sealing devices 16according to this invention are subjected to inwardly andoutwardly'directed centripedal acceleration forces as is fully explainedin the US. Pat. to Jones, No. 3,456,625. Thus, in the area of minor axisof the housing or lobe junction 90 each blade means 40 is subjected to anegative acceleration force or inwardly directed centrifugal forceQAtrelatively low angular velocities of rotor 12, the pressure of fluid inpressure chamber 78 acting upon pistons 56 'in a direction toward rotorend faces 38 exerts a force on each piston which is insufficient toovercome the counteracting force exerted by spring 66. The effect of theforce of spring 54 on pistons 56 is negligible because of theshallowness of inclined edges 62. Thus, until a predetermined high rpmof rotor 12 is reached, pistons 56 are unable to retract and disengageblade means 40 from trochoidal surface 20. As the rotor rpm increasesthe pressure of fluid in pressure chamber 78 increases. Also, as rotorrpm increases, the centrifugal force acting inwardly upon blade means 40increases. When a predetermined rotor rpm is reached, the fluid pressurein pressure chamber 78 is of such magnitude that the force exerted oneach of the pistons 56 is sufficient to overcome the force of spring 66so that, when blade means 40 is moved inwardly in the area of lobejuncture 90 under the inwardly directed centrifugal force, pistons 56are moved toward rotor end faces 38 and arms 60 are wedged between thepin 64 and the bottom wall of slot 74. This wedging action holds theblade means 40 in a retracted position as rotor rpm increases above thepredetermined value, thus reducing friction at the higher rpm whensealing contact is less necessurface in spite of the varying directionof centrifugal force acting upon the blade means. The fluid pressurizedactuating means 44.0t" each sealing device 16, will hold the associatedblade means 40 captive until rotor rpm and, hence, fluid pressure inpressure chamber 78 falls below the predetermined values and the forceof springs 66 is sufticient to overcome theforce exerted on pistons 56by the fluid pressure. Under the urging of springs 66, each piston ismoved away from the rotor side face 38, thus releasing tabs 46 formovement toward trochoidal surface 20 under the centrifugal forceexerted thereon in the area of lobe junction 90.

reto. Various changes can be made in the arrangement of parts withoutdeparting from the spirit and scope of the invention as the same willnow be understood by 'those skilled in the art.

. What is claimed is: l

1. In a rotary mechanism of the type comprising a housing having aninner peripheral wall of trochoidal shape and end walls defining acavity therebetween and a rotor supported for eccentric rotation withinthe cavity and defining with said housing walls a plurality of workingchambers which successively expand and contract in volumetric size asthe rotor rotates, the rotor having apex portions and sealing devicescarried in the apex portions, each sealing device comprising:

a. a blade means disposed for reciprocative move ment in a groove in anassociated apex portion of the rotor;

b. biasing means for urging said blade means into en gagement with theperipheral wall, and

c. a pressurized fluid actuating means responsive to the angularvelocity of the rotor and coacting with the seal blade to achievedisengagement of the seal blade with theperipheral wall at a rotorangular velocity above a predetermined value.

2. The apparatus of claim 1 wherein the pressurized fluid actuatingmeans includes a linear motor means connected to a source of pressurizedfluid, the pressure of which varies in direct proportion to thevariation in the angular velocity of the rotor.

3. The apparatus of claim 2 wherein said motor means is two piston andcylinder mechanisms. 4. The apparatus of claim 1 wherein saidpressurized fluid actuating means includes lubricating pump means.

5. The apparatus of claim 1 wherein the pressurized fluid actuatingmeans includes two pistons disposed for reciprocative movement incylindrical bores extending it is believed now readily apparent that thepresent in the rotor parallel to the axis of rotor rotation, and whereinsaid blade means includes spaced radially extending projections each ofwhich is engageable by a piston to maintain the blade means out ofengagement with the housing peripheral wall at rotor angular velocityabove a predetermined value.

6. In a rotary mechanism of the type comprising a housing having aninner peripheral wall of trochoidal shape and end walls defining acavity therebetween and a rotor supported for eccentric rotation withinthe cavity and defining with said housing walls a plurality of.

working chambers which successively expand and contract in volumetricsize as the rotor rotates, the rotor having apex portions and sealingdevices carried in the apex portions, each sealing device comprising:

a. a blade means disposed for reciprocative movement in a groove in anassociated apex portion of the rotor; v

b. biasing means for urging said blade means into contact with saidperipheral wall;

c. a piston and cylinder motor means in said rotor disposed so that thepiston is engageable with said blade means;

d. a source of pressurized fluid, the pressure of which varies as .afunction of the angular velocity of the rotor;

e. passageway means communicating said source of pressurized fluid withsaid piston and cylinder means to effect actuation of the piston intoengage ized fluid exerts a force on each piston tending to move thepiston outwardly from the centerline of the rotor extending normal tothe rotor axis of rotation.

9. The apparatus of claim 6 whereinthe said. piston and cylinder meansincludes a wedging means coacting with said blade means to preventradial outwardly directed movement of the blade means when said.predetermined fluid pressure is attained.

10. The apparatus of claim 9 wherein said blade means includes inwardlyextending tab means engageable by said wedging means.

11. The apparatus of claim 10 wherein said tab means comprises anelongated arm and stop element carried in said arm to be engaged by saidwedging means.

12. The apparatus of claim 6 wherein said piston and cylinder motormeans comprises two pistons disposed in a cylindrical bore in the rotorand arranged in juxt-. aposed position for reciprocative movement, eachpiston carries an axially extending wedging means coacting with saidblade means to prevent radial outwardly directed movement of the blade.means when said predetermined fluid pressure is attained.

13. The apparatus of claim 12 wherein said blade means includes twoaxially spaced radially extending tabs each of which has a stop elementadapted to be en inner side of the arm has an inclined surface whichextends in a direction radially outward of the associated pistonrelative to the apex portion of the rotor.

l6.'The apparatus of claim 12 wherein each piston is spring biased in adirection away from coaction with said blade means, said spring beingselected to permit piston movement upon said predetermined pressurizedfluid pressure.

1. In a rotary mechanism of the type comprising a housing having aninner peripheral wall of trochoidal shape and end walls defining acavity therebetween and a rotor supported for eccentric rotation withinthe cavity and defining with said housing walls a plurality of workingchambers which successively expand and contract in volumetric size asthe rotor rotates, the rotor having apex portions and sealing devicescarried in the apex portions, each sealing device comprising: a. a blademeans disposed for reciprocative movement in a groove in an associatedapex portion of the rotor; b. biasing means for urging said blade meansinto engagement with the peripheral wall, and c. a pressurized fluidactuating means responsive to the angular velocity of the rotor andcoacting with the seal blade to achieve disengagement of the seal bladewith the peripheral wall at a rotor angular velocity above apredetermined value.
 2. The apparatus of claim 1 wherein the pressurizedfluid actuating means includes a linear motor means connected to asource of pressurized fluid, the pressure of which varies in directproportion to the variation in the angular velocity of the rotor.
 3. Theapparatus of claim 2 wherein said motor means is two piston and cylindermechanisms.
 4. The apparatus of claim 1 wherein said pressurized fluidactuating means includes lubricating pump means.
 5. The apparatus ofclaim 1 wherein the pressurized fluid actuating means includes twopistons disposed for reciprocative movement in cylindrical boresextending in the rotor parallel to the axis of rotor rotation, andwherein said blade means includes spaced radially extending projectionseach of which is engageable by a piston to maintain the blade means outof engagement with the housing peripheral wall at rotor angular velocityabove a predetermined value.
 6. In a rotary mechanism of the typecomprising a housing having an inner peripheral wall of trochoidal shapeand end walls defining a cavity therebetween and a rotor supported foreccentric rotation within the cavity and defining with said housingwalls a plurality of working chambers which successively expand andcontract in volumetric size as the rotor rotates, the rotor having apexportions and sealing devices carried in the apex portions, each sealingdevice comprising: a. a blade means disposed for reciprocative movementin a groove in an associated apex portion of the rotor; b. biasing meansfor urging said blade means into contact with said peripheral wall; c. apiston and cylinder motor means in said rotor disposed so that thepiston is engageable with said blade means; d. a source of pressurizedfluid, the pressure of which varies as a function of the angularvelocity of the rotor; e. passageway means communicating said source ofpressurized fluid with said piston and cylinder means to effectactuation of the piston into engagement with said blade means to holdthe latter from contact with the inner peripheral wall upon apredetermined fluid pressure which is a function of rotor rpm.
 7. Theapparatus of claim 6 wherein said source of pressurized fluid is alubrication pump drivably connected to the rotor.
 8. The apparatus ofclaim 6 wherein said piston and cylinder motor means comprises twopistons disposed in a bore in the rotor extending parallel to the rotoraxis and wherein both pistons are Exposed to pressurized fluid in acommon pressure chamber so that pressurized fluid exerts a force on eachpiston tending to move the piston outwardly from the centerline of therotor extending normal to the rotor axis of rotation.
 9. The apparatusof claim 6 wherein the said piston and cylinder means includes a wedgingmeans coacting with said blade means to prevent radial outwardlydirected movement of the blade means when said predetermined fluidpressure is attained.
 10. The apparatus of claim 9 wherein said blademeans includes inwardly extending tab means engageable by said wedgingmeans.
 11. The apparatus of claim 10 wherein said tab means comprises anelongated arm and stop element carried in said arm to be engaged by saidwedging means.
 12. The apparatus of claim 6 wherein said piston andcylinder motor means comprises two pistons disposed in a cylindricalbore in the rotor and arranged in juxtaposed position for reciprocativemovement, each piston carries an axially extending wedging meanscoacting with said blade means to prevent radial outwardly directedmovement of the blade means when said predetermined fluid pressure isattained.
 13. The apparatus of claim 12 wherein said blade meansincludes two axially spaced radially extending tabs each of which has astop element adapted to be engaged by a wedging means of a piston toprevent radial outwardly directed movement of the blade means when saidpredetermined fluid pressure is attained.
 14. The apparatus of claim 13wherein said wedging means comprises an arm axially projecting from eachof the pistons and bifurcated to embrace a tab of said blade means sothat the stop element engages the radially inner side of the arm. 15.The apparatus of claim 14 wherein said radially inner side of the armhas an inclined surface which extends in a direction radially outward ofthe associated piston relative to the apex portion of the rotor.
 16. Theapparatus of claim 12 wherein each piston is spring biased in adirection away from coaction with said blade means, said spring beingselected to permit piston movement upon said predetermined pressurizedfluid pressure.